Carburetor



March 2, 1943. v, R. HEF'i'LER CARBURETOR 4 Sheets-Sheet 1 Filed July 30, 1940 March 2, 1943. v H F 2,312,816

CARBURETOR Filed July 30, 1940 4 Sheets-Sheet 2 I N \"ENTOR.

March 2, 1943. v HEFTLER 2,312,816

' CARBURETOR Filed. July 30, 1940 4 Sheets-Sheet 5 INVENT R.

- March 2, 1943. R;v HEFTLER 2,312,816

' CARBURETOR Filed July 30, 1940 4 Sheets-Sheet 4 INVENTOR Patented Mar. 2, 1943 UNiTED STATES PATENT OFFICE CARBURETOR Victor E. Heftler, Grosselointe Park, Mich.

Application July 30, 1940, Serial'No. 348,431

6 Claims. (01. 261-69) It is an object of this invention to provide a carburetor of the double Venturi type having a mixture conduit of such a design as to permit accurate machining of the air swept surfaces of said conduit.

It is a further object of this invention to provide in a downdraft carburetor an idling by-pass so shaped as to hold an excess charge of fuel for use in starting the engine, or upon the engine resuming normal operation after deceleration.

It is a further object of this invention to provide a sensitive device for cutting off the supply of fuel when the engine is decelerating.

It is a further object of this invention to provide an improved accelerating pump.

Fig. l is an elevation, viewed from the lower side of Fig. 2.

Fig. 2 is a top plan view, with one half of the cover removed.

Fig. 3 is an elevation, viewed from the top side of Fig. 2, with some parts cut away.

Fig. 4 is an elevation, viewed from the right side of Fig. 2 with some portions in cross-section along parallel lines to, 4b, 4c and 4d of Fig. 2.

Fig. 5 is a partial cross-section along line 5-5 of'Fig. 2 and viewed in the same direction as Fig. 9.

Fig. 6 is a partial cross-section along line 6-6 of Fig. 2.

Fig. 7 is a diagrammatic schem illustrating the complete idling system.

This invention is described as applied to a down draft carburetor, which comprises a downwardly discharging throttle housing member 2|, provided with a flange 22 for attachment to an engine manifold (not shown) in the well'known manner. The throttle housing member 2| supports a mixing chamber body member 23, which, in turn, supports a cover member 24, these three main parts being suitably fastened to one another, by screws 25 for instance. A heat insulating gasket 52 is preferably inserted between the throttle housing member 2| and the mixing chamber body member 23.

The entire air supply enters through a conduit 26 in the cover member 24 (Fig. 1) controlled by a choke valve 21 mounted on shaft 28 to which is fastened choke lever 29, to be actuated in any one of the Ways now current and well known in the art. Conduit 26 registers with conduit 30 in the mixing chamber body member 23, which leads to conduit 3| in the throttle housing member 2|. A throttle valve 32, mounted on shaft 33, controls conduit 3| to restrict more or less the free passage of mixture to the engine associated with the carburetor. The means used to rotate the throttle are not shown and may consist, as in most automobiles, of a lever fastened to the throttle shaft and actuated by the driver according to his wishes for more or less speed or power. The movement of the throttle is limited by means of stop lever 34, fastened on shaft 33, and provided with two lugs 35 and 36. When the throttle is opened wide, lug 35 comes in contact with stop pin 31, which may be cast integral with the throttle housing member 2|. To control the so-called closed position of the throttle, a screw 38 is threaded in lug 36, its end being adapted to contact a combined yielding stop and valve 39. The word closedj, although used universally in carburetor parlance, is not strictly accurate: if the throttle'were closed so tightly that no air could pass, the engine would stall; to avoid this, it is customary to prevent the complete closure of the throttle so as to leave, between the edge of the throttle and the bore in throttle housing member 2|, a narrow opening just sufiicient to admit enough mixture of fuel and air to keep the engine running at slow speed, or idling, as it is called; The amount of mixture necessary for idling varies with the engine, and, on a given engine, varies with its condition, therefore, the .position of the throttle for idling should be ad-, justable, as is done by means of screw 38.

Formed in the mixing chamber body member 23 is a constant level fuel chamber 62. A fuel supply pipe (not shown) may be connected to the threaded inlet 63, leading to a needle valve which is actuated, in the well known manner, by a level sensitive device, in this case a pair of floats symmetrically located with reference to line 44 of Fig. 2, where one of the floats is shown in plan at 65, the other a being shown in elevation in Fig. 3. The parts are so made and proportioned that liquid fuel will fill the chamber to the level of line L-L in Figs. 3 and 6.

A calibrated orifice Bl allows fuel to flow into chamber 68 and hence, through main jet tube 69, to the annulus 60. Shank 45 of the second Venturi holder is drilled at H! to a diameter larger than the outside of main jet tube 69, thus leaving a tubular passage H around said main jet tube. V The diameter of shank 45 is reduced, below shoulder 46, to a diameter smaller than that of hole 12, so that there is formed another tubular passage Ha, concentric with ll, and leading from chamber 13. A main well 14 (Fig. 3) is drilled vertically, somewhat ofi the'vertical plane 4-4 of Fig. 2, but close enough thereto to intersect hole 2 at 15, where it connects with tubular passage Ha. Well 14 is opened to the air in the top of the fuel chamber, preferably through a calibrated opening 16 in removable main vent piece T1. At some distance below the fuel level L-L and in plane 6-9 of Fig. 2, a communicating passage 18 (Fig. 6) is drilled, intersecting main well 14, and opening into chamber I3 at 19. A threaded member 89, whose slotted head is visible in Figs. 2 and 3, is provided with a calibrated orifice to afford a controlled fuel feed from the fuel chamber 62 to the passage 78. This member 89 is diagrammatically indicated on Fig. 6, although, strictly speaking, it is not visible on this crosssection as it lies entirely in front of the plane of the figure.

The suction obtaining in annulus 60 draws solid fuel through main jet tube 99 and, through tubular passage H and chamber 13, will draw air from main well 74 to form an emulsion with fuel drawn through the calibrated orifice of piece 913. The man skilled in the art will readily recognize "the method of obtaining a correct mixture by the combining of two fuel feeds as the well known one disclosed in U. S. Patent907,'9153.

when the throttle is in idling position, the suction in the second venturi becomes 'insuificient to lift any fuel 'up to the annulus 69, but an,"i'dling by-p'ass is resorted to to supply fuel to. the engine. This idling by-p'ass takes the form of an inverted U, with one branch extending from a calibrated fuel orifice below -the fuel level to an horizontal connection above said fuel level with the other branch which leads downwardly to the proximity of the throttle. The drilled hole '18 is adapted to receive and to be closed by the end of idling supply piece 81. A calibrated hole 94 is drilled in the tip of said piece 8!, which is also cross-drilled, so that fuel, 'liinitedly supplied throughcalibration 84, may reach the tubular passage 95. between piece 81 and hole 82. Hole 82 is plugged against leakage by plug 83. Vertical -hole 8'9, Fig. ti, intersects this tubular passage to bring into it air from air conduit 39 through hole '81, the effective area of which may be regulated by meansof the idling adjustingscrew The top of hole 8'6 is covered by the base of cover member 2 3 and is closed thereby. The idling by-pass has its beginning or origin at the tubular passage 83, close to the calibrated hole 84 which measures fuel thereto and well below the levlfL-L of the fuel. It is made up of vertical hole 99, horizontal connecting hole 99 and hole 9! leading downwards and connecting with passage 92 which opens into chamber 93, connectedwith the main mixture passage through ports94 and 95 bestriding the edge of the throttle when the latter is in closed position. When the engine is at rest, idling well 88 is filled with solid fuel up to line L'L, and so is channel 89. Upon starting the engine with the throttle in idling position, this solid fuel will be drawn through the idling passages towards chamber 93 before normal idle feed is established. After the first few strokes of the engines, air measured at 81 comes down well 86 to mix with the fuel passing through calibration 84, forming an emulsion which flows through the inverted U tube 89, '99, 9| towards chamber 93. This initial charge of pure fuel standing in '86 and 89 is very useful in starting. Another advantage is found in the rapidity with which the idling channels will resume their normal working upon returning to idling speed: When the engine is running with the throttle opened well beyond 76' the idling position, the fuel flowing through the calibrated orifice in piece will be urged away from the idling channels towards annular passage H and the second venturi and there may be a reverse flow of air from main conduit 3| through holes '94 and into chamber 93, through the idling channels into channel 18, because the suction at the double venturi is greater than the suction ports 94 and 95. If then the throttle be suddenly closed and the load disconnected, as when the clutch of an automobile is disengaged, the motor will slow down rapidly and will stall unless the idling by-pass resumes its function quickly enough. Immediately as the throttle is closed, the suction at the main venturi drops so low that no fuel is delivered at that point, but the high manifold suction is transmitted to passage 92 and air, entering at 87, flows at once through the idling by-pass. As soon as fuel from calibrated hole 84 meets this air stream, it will be picked up by it and carried "to the engine. By'adrnitting air into the idling 'by-pas's at a point close to said by-pass beginning, the time necessary to resume normal idling is reduced to 'a minimum, and stalling from this cause prevented.

If the throttle is closed from ahalf open position, for instance, 'the inertia of the engine and of its lo'a d prevents "its speed from decreasing at once 'to the idling speed, so that, during this deceleration period, the suction -in chamber 93is abnormally high, which results in an increased pull on the fuel supply at idling calibration "8 1 so that too rich a mixture is delivered to the engine, and that at a time when no power is required. Such excess fuel produces obnoxious fumes and is wasted; this happens when an automobile coasts down to a stop or downhill. To obviate this defect, it has been proposed-to utilise the abnormally high suction to operate a valve admitting air into the idling channels. See the French patent to 'Waseige No. 545,073, Fig. '1. If this admission of air is large enough, it will satisfy the suction in theidling by-pass, and no fuel will be fed therethrough. Ijhave found that, on an inch and a quarter carburetor,

it was necessary to use an air admission of ths of an inch to completely prevent the feeding of fuel. The present invention comprises 'certain improvements on this principle to make the operation positive and rapid and also to prevent this operation unless the throttle is in the idling position. It is necessary toopen the hole that admits air into the idling channels 'com pletel-y as soon as the need for it arises, otherwise, if theparts were to remain for an apreciable length of time in an intermediate position, the idling channels would continue to feed a diminished amount of fuel and a weak mixture would be fed to the engine, with'the well known drawbacks of a weak and slow burning mixture, such as backfire and pitting of the,

intake valves. It must be recognized that the normal vacuum in the manifold, or fdown-" stream of the throttle, and here norm'aP' means the vacuum when the engine 'is driving the car and not decelerating, does not decrease at once upon opening the throttle. Tests on a particular car have shown a vacuum of 18" of mercury at 10 miles per hour, rising to amaximum of 19 at 25 miles per :hour todecrease again to 18" at 37 miles and to 12" "at 65. If the admission of air was dependent only on manifold vacuum and was regulated to occur for a vacuum 0f say 18. /2f, one half inch more than to the back of the pilot piston.

the normal idling vacuum, it would also occur when the car is running normally at speeds between 15 and 35 miles per hour. This would upset the carburetion at a critical time in the operation of the carburetor when fuel feeding is being transferred progressively from the idling system to the double venturi.

Adapted to slide in bore 91 machined in the throttle housing body member 2| is the operating piston 98 (Fig. 3), which is urged upwards by the spring 99. The lower portion of bore 91 communicates through hole I with the main conduit 3I below the throttle. so that the vacuum that obtains there would pull the piston downwards against the spring, were it not for the fact that this vacuum is also impressed on the top of the piston through the small aper-. ture IOI. At right angle to this bore 91, and shown on Fig. 4, is a pilot piston I02, slidable in bore I03, said bore being closed on the right by plug I04 forming a stop for the pointed head of the piston and closed at the other end by gland I05, in which is threaded screw I06 for.

adjusting the tension of spring I07. The head of this piston is exposed to atmospheric pressure through channels 96 and I09. A passage IIO leads from the space above the head of the operating piston 98 into the bore I03, close to the head of pilot piston I02, but covered thereby when the carburetor is at rest. In the diagram of Fig. '7, the two bores 91 of the operating piston and I03 of the pilot piston are of necessity shown with their axes in the same Plane. In the working construction, bore 91 is vertical, as in the diagram and is shown in section in Fig. 3, but bore I03 is horizontal and perpendicular to the plane of Fig. 3, its axis being at the center of plug I04 which closes it. In the diagram, passage IIO is radial to both bores, in the construction illustrated, it is radial to bore 91 of the operating piston and tangent to the bore I03 of the pilot piston, so that, due to the elongated shape of the opening made by passage IIO into bore I03, it will not be necessary that iston I 02, acting like a slide valve, uncovers said opening completely to obtain as effective a communication between the two bores as the diameter of passage IIO permits. With the parts in the position shown, piston I02 closes passage I I0, and atmospheric pressure is not transmitted therethrough to the space above the head of operating piston 98. On the contrary, this space is subjected, through small aperture IOI, to the same vacuum as is impressed upon the underside of piston 98. Because of this equalization of the pressures on both sides of the piston, spring 99 need not be very strong to hold it in and return it to its position.

The combined stop and valve 39 (Fig. 4) is provided with two conical surfaces 2 and H3 adapted to co-operate with corresponding valve seats in the stop housing H4 cast integral with the throttle housing body 2|. A channel II5 connects the pilot piston bore I03 with chamher He located between the two valve seats. Channel III leads from the down stream side of the throttle to the space in stop housing H4 adjacent the seat for valve surface H2 and channel 8 leads from the upstream side of the throttle to the space adjacent the seat for valve surface II3. When the throttle is in the idling position, as shown, the throttle stop screw 38 holds valve surface II2 off its seat so that the manifold vacuum, taken downstream of the throttle through III, is impressed through II5 Spring I0'I is adjusted so as to prevent any movement of the pilot piston I02 as long as the manifold vacuum does not exceed the normal idling vacuum. During deceleration, the vacuum is higher than normal, and, provided the throttle be closed and valve 39 in position to open channel II5 to. the manifold vacuum, the pilot piston I02 will move to the left and uncover hole IIO, whereupon the upper side of piston 98 will be subjected to nearly atmospheric pressure transmitted through IIO, I09 and 96, thus destroying the balance between the pressures above and below the piston. The suction below the piston will pull it downwards to the limit of its travel because of the weakness of spring 99. In this movement the groove II I of the operating piston comes into registration with hole 96, so that air is admitted into chamber 93, thus cutting out the suctiononthe idling channels so that no fuel is delivered to the engine.

Aperture IOI need not be over %4th of an inch to transmit the vacuum from one side of the piston 98 to the other; assuming that pas sage H0 is of the same diameter, its flow ca-f pacity will be nearly equal to that of aperture IOI, so that, when said passage H0 .is opened to atmospheric pressure, the vacuumabove pis ton 99 will be reduced to approximately one half of the vacuum below it. Assuming that spring is so proportioned and adjusted as to begin to open passage IIO when the manifold vacuum reaches 18 /2 inches of mercury and that the rate of said spring is such that the passage will be fully opened for an increase in vacuum of one half inch, the full opening of this passage will cause a decrease of 9 inches in the vacuum above piston 98, which will then move downwards a great deal farther than would be the case if it were subjected directly and solely to the manifold vacuum on one side and to atmospheric pressure on the other.

Upon reopening of the throttle, the valve 39 moves to the right, the space at the left of the pilot piston is no longer connected to the downstream side of the throttle, but to the upstream side, through channel II8, where the suction is much lower. The opening of this connection breaks the vacuum so that the spring I0'I can force the pilot piston back to its initial position whereupon operating piston 98 is also returned to normal position and normal idling is resumed. During the deceleration, fuel has accumulated in the idling well 86 up to the line LL and in channel 89 up to a slightly higher level; this small charge of excess fuel is very useful in avoiding any hesitation when normal running is resumed.

It is clear that some other form of suction operated device capable of opening at atmospheric vent could be used, as a pilot valve, in place of the structure described, which is only my preferred form. I base this preference upon the fact that in this slide type of valve the opening and the closing of aperture III) will occur for the same value of the suction. In other words, if, as assumed earlier, spring I0'I is so set that the piston I02 will begin to uncover passage III! when the increasing suction reaches 18 of mercury upon decelerating, then, when the speed has decreased to such an extent that the suction reaches the same value of 18% on the way down towards normal, the pilot piston will close passage II9 so as to cause normal operation to be resumed. In other types of valves responsive to suction and often vem- -goloyedin carburetors, there is :a difference between the values of the suction for which it opens. and for which it closes. In such a case, in order to insure that normal operation will resume. for 18 of suction, it might be necesha'ryto set the spring :so that 20 of suction needs to be reached before the valve opens to cause degassing to take place. In other words, the degassing would have to be delayed to insure that the regassing be brought about be- .fore the motor speed drops too low.

. I claim:

..1. In a carburetor, a main air conduit, an idling by-pass discharging into said conduit, :an operating valve normally under the influence of manifold vacuum on both sides thereof, means opened by said valve to admit air into said idling by-pass, and means to admit air on one side of said valve to cause its operation.

2. In a carburetor, a main air conduit, a throttle therein, an idling by-pass discharging into said conduit, an operating valve normally under the :infiuence of manifold vacuum on both sides thereof, means opened by said valve to admit air into said idling by-pass, a pilot valve, throttle-and vacuum controlled means to operate said pilot valve, and means operated thereby to admit air on one side of said operating valve to cause its operation.

3. In a downdraft carburetor, a constant level fuel supply chamber, a main mixture conduit, a throttle therein, a main fuel feeding system, an idling by-pass having its origin below the level of the fuel at the main fuel feeding system and adapted to draw fuel therefrom and leading into said mixture conduit in proximity to the t'i'irottle, said idling 'by-passbeing of inverted U shape, and means to admit air into said bypass in close proximity to its origin.

4. In a carburetor, a main air conduit, a throttle therein, an idling -by-pass discharging into said conduit, an-oper-at-ing valve normally under the influence of manifold vacuum on both sides thereof, means opened by said valve to admit air into said idling by-pass, a valve chamber, a vacuum controlled .pilot valve therein and a port in said valve chamber communicating with one side of said operating valve and normally covered by said pilot valve.

:5. In a carburetor, a main air conduit, a throttle therein, an idling by-pass discharging into said main air conduit, an operating valve constantly under the influence of the manifold vacuum on one side, a restricted vacuum connection to the other side of said valve, means opened by "said valve to admit air into said idling lay-pass, a valve chamber, a vacuum controlled valve therein and a port in the wall of said valve chamber communicating with the second mentioned side of the operating valve to admit air thereto and normally covered by said second mentioned valve.

6. In acarburetor, a'mai-n air conduit, a throttle therein, an idling by-pass discharging into said conduit, an operating valve normally under the influence of manifold suction on both sides thereof, means opened by said valve to admit air into said idling by-p-ass, a pilot valve under the influence of said maniioldsuction and means opened thereby to admit air to one side of said operating valve to cause its operation.

VICTOR R. HEF'ILER. 

